462 MR. F. B. BEDDARD ON THE [ISTov. 28, 



Artei'ial System. — The arrangement of the aortic arches is pre- 

 cisely like that of the Lacertilia. It is not so difi'erent from that 

 of Lacerta, Iguana, tkc. as is the arrangement found in Varanits. 

 The carotid arch gives off the usual three branches before joining 

 posteriorly the aortic arch. The third branch, that to the 

 muscles of the shoulder, arises just before the carotid arch joins 

 the aorta. 



As to the systemic (aortic) arch (see text-fig. 59), it is in- 

 teresting to note that on both sides this arch gives ofl' an 

 (esophageal artery ; freqviently, as is well known, the light arch 

 alone gives off such a branch. Just at the meeting of the two 

 aortse the subclavians arise. A careful dissection shows (see 

 text-fig. 59, S'cl.) that both subclavians arise close to each other — 

 and one a little in advance of the other — from the right aortic arch 

 only just before it joins the left. Each subclavian gives ofi' im- 

 mediately after its origin a forwardly directed vertebral artery, 

 which plunges at once into the parietes. Immediately after the 

 junction of the two aortse arises the first pair of intercostals. 

 Between this pair and the next arises a gastro-cesophageal artery. 

 This artery is separated from the gastric by three paii's of inter- 

 costals, and five pairs of intercostals lie between the gastric and 

 the superior mesenteric artery. The intestinal arteries I need 

 not refer to, as they have been already treated of by 

 Hochstetter *. 



It may be mentioned that, as in some other Lizards (e. g, 

 Gerrhosaurus t), the pulmonary arch gives off on each side a 

 branch which runs along the windpipe and sends off branches to 

 the thyroid. 



Ve^ioits Sy stein. — There is no question that, apart from details, 

 the venovis system of Hatteria is distinctly Lacertilian. Nor 

 do the dift'erences which it shows from Lacertilia tend to prove 

 a nearer resemblance to the Chelonia or to the Crocodilia. On 

 the other hand, I believe it possible to detect likenesses to the 

 Ophidia. This, however, in my opinion, does not argue a special 

 affinity between Hatteria and the Ophidia, but the antiquity of 

 the Hatterioj type, which pala?ontology, as is well known, has 

 proved. 



The Lacertilia are distinguished by the double vena cava 

 posterioi', which is double, that is to say, as far forward as the 

 gonads, from which point onwards there is but a single ti'unk 

 formed by the fusion of the two trunks. As a rule, also, there is 

 an asymmetry between the two venae cavpe, or efferent I'enals, 

 as they are commonly termed. When there is this difference, 

 the right vessel is of greater calibre than the left. In Hatteria we 

 meet with the same conditions, and here the left vena cava is of 

 distinctly less calibre than the right. The two vessels, moreover, 



* Morph. Jahib. vol. xxvi. p. 217. 



t Beddai'd, "Anatomy of Gerrhosaurus" P. Z. S. 1905, vol. ii. p. 263, text- 

 fig. 37, P. 



